SALTA, Argentina -- Their facial features are clear, and their muscles are firm. The blood remains frozen in their veins, and the vivid clothes they wore the day they died remain intact.

The three Incan children -- believed to be victims of a mountaintop sacrifice about 500 years ago -- are among the best-preserved mummies ever found, and Argentine officials hope to put them on display this fall in a museum in this city in the far north.

But not everyone is looking forward to the public unveiling of human remains that look anything but ancient. Members of an Argentine indigenous organization are trying to legally block the display, saying it dishonors their "little brothers and sisters." Rival museum officials in Buenos Aires dismiss the exhibit as morbid. And the explorer who discovered the bodies six years ago worries that a rushed showing could permanently damage them.

"I'd much prefer that they not be displayed, just because of all of the headaches," said Johan Reinhard, who lives in Arlington and is an explorer in residence for the National Geographic Society, which sponsored the expedition.

Reinhard and his team of mountaineering archaeologists found the three bodies, along with dozens of Incan artifacts, atop the 22,000-foot Llullaillaco peak near the Argentine border with Chile, about 200 miles west of here.

The corpses -- two girls and a boy believed to range in age from about 6 to 15 -- were not artificially mummified, but preserved naturally by the combination of freezing temperatures, thin air and moderate humidity. No signs of violence were found; scientists suspect the three were simply left to freeze to death on a funerary platform as sacrificial gifts to an ancient mountain god.

After National Geographic's one-year exclusivity rights to the mummies and artifacts expired, the Argentine government took possession of them. Officials decided to open an Inca-themed museum in Salta to display the finds and inaugurated the Museum of High Altitude Archaeology last November in a remodeled 19th-century Victorian building bordering the city's central square.

The museum currently exhibits the collection of artifacts -- including gold and silver statues, textiles and pottery -- and hopes to unveil a mummy exhibit for its one-year anniversary on Nov. 19, charging tourists about $3 to enter. The museum plans to show the mummies in rotation, one at a time.

"Whether it was right or wrong to take the mummies from the mountain, I don't know," said Gabriel Miremont, the museum's director. "But we now have them, so we have a choice: leave them in a laboratory with a small group of scientists, or share them with society. I think it's more democratic to give everyone the opportunity to see them."

Since taking possession of the corpses, the museum has solicited the support of several local indigenous leaders. Miremont said they were skeptical at first but changed their minds after assurances that the exhibit would honor the dead, not exploit them.

But the country's first and largest association of native tribes strongly opposes the exhibit, and its president said last week that the group's lawyers have begun the process of trying to prevent the display from opening. He said he would like to see the mummies returned to the mountain.

"These children have been taken violently from their sacred resting places, and we consider this an attack on our people," said Rogelio Guanuco, president of the Indigenous Association of Argentina, which says it represents 65 percent of the country's 868 native communities. "The desire to show them is something we consider even worse, because it turns something spiritual into something commercial."

It isn't clear exactly where the children lived before making the arduous trek to the mountaintop, which makes it difficult to determine which modern native group can claim the right to speak for them. Reinhard said the children might have traveled with an entourage from Chile to the Argentine mountain peak -- a possibility that would add jurisdictional complexities.

Because not all native cultures considered their sacrificial dead as untouchable, sacred objects, the uncertainty of origin also clouds the ethical debate.

"They buried these, but we know that they also periodically brought some others out for display, to be honored publicly," said Reinhard, whose previous high-altitude expeditions uncovered 18 sets of human remains.

His most famous discovery was the mummified Peruvian "ice maiden" known as Juanita, a pre-Columbian teenager apparently also sacrificed to the Inca gods on a mountaintop. When Juanita was displayed at the National Geographic Society in Washington in 1996, President Bill Clinton joked that she was so attractive, "If I were a single man, I might ask that mummy out."

Increasingly, experts favor keeping human remains under wraps, particularly if they belong to native groups. In recent years, many museums throughout the world have returned -- or "repatriated" -- human artifacts to native groups that have requested them. The National Museum of Natural History, for example, has to date repatriated about 3,300 Native American remains and 88,000 funerary objects, according to its Web site.

Jose Antonio Perez Gollan, director of the Ethnographic Museum of the University of Buenos Aires, is among the officials who have publicly called for repatriation of the Salta mummies. Putting remains on display panders to the worst instincts of the morbidly curious, he said, and offers little educational value.

"I don't think this is the way to try to learn about indigenous cultures," Gollan said. "It doesn't help at all."

When visitors view the mummies, they will look through a window into a chamber that aims to replicate the exact atmospheric conditions of the mountain -- a temperature of 0 degrees Fahrenheit, 45 percent humidity and very little light and oxygen. Workers are still putting the finishing touches on the windows, but Miremont is hopeful they will meet the November target date.

Reinhard, who heads a scientific consulting group formed to oversee the work, said the museum has proceeded with design plans without input of his committee. He said he was worried that the chamber and the viewing windows will not be properly tested before the public debut. It can take years for a very small change in atmosphere to be detected if there is even a very minor leak, he said, by which time irreparable damage can be done.

"It's very, very easy to run into problems with displays," Reinhard said in a telephone interview. "The preservation of these mummies is incredible -- there's nothing else like them in the world. So much care has gone into them . . . it would be a shame if that came to a stop now."

But that doesn't mean he opposes the exhibit on ethical grounds. He said he believes viewing mummies can help people make profound connections with cultures they never really considered before, and that such strong links can have an immeasurable educational value.

"There's nothing quite like the authenticity that comes with seeing a real person," Reinhard said. "You can have a replica displayed, but it just doesn't have that same emotional power."